Central heating strategy

[Gary27]

I have a Vailliant 418 with weather compensation and have always had a problem with it cycling. Although via certain user adjustable settings and ensuring I have an adequate water flow on occasion I still have problems.

Just for interest I decided to try a different approach. My logic for thinking this might be a viable option is that a condensing boiler likes to run cool (output) and also they are most efficient on low output (modulated down). Both of these should lead the boiler to running efficiently.

So what I have done it down rated the output to 5kw and just let the boiler heat the house slowly. It seems to take about 2hrs to reach room temperature. I need to ensure the output will heat the house which it does. The question is why can't I just let it reach temperature quickly and modulate down. I can but it on occasion it goes over temperature and can get in a cycling mode which drives me mad.

The question is is there a reason not to do what I have tried?

Gary

 

[Andygasman2010]

http://vaillantcyclingproblem.blogspot.co.uk/

If you rename this post, or make a new one, call it something like "Vaillant 400 series, weather compensation, cycling" more people will will read it as it's been the subject of great discussion on here!

Also try searching the forum.

 

[Gary27]

http://vaillantcyclingproblem.blogspot.co.uk/

If you rename this post, or make a new one, call it something like "Vaillant 400 series, weather compensation, cycling" more people will will read it as it's been the subject of great discussion on here!

Also try searching the forum.

Its not the cycling I wanted to bring up, I have looked at that to death on this site and it has helped, its more the running at a low output.

 

[Andygasman2010]

I have an Ultracom CXi with weather compensation (similar software to yours)

I find it better to have longer heating periods at a lower heat curve/KWs with 3 degrees lower set-back periods.

Thing is, every house is different. Depends on how well insulated it is.

Best case scenario would be a well insulated box!

 

[Agile]

It also depends on how concerned the owner is about using more gas than absolutely necessary.

If you dont need heating overnight ( like me ) then its more efficient turning the boiler on at 6.45 with a higher power setting instead of a lower power and turning it on two hours early and losing two hours of heating cost.

Or you can do what I do and change the max power setting from time to time during the day! But thats a bit anorackish!

Tony

 

[Gary27]

I have an Ultracom CXi with weather compensation (similar software to yours)

I find it better to have longer heating periods at a lower heat curve/KWs with 3 degrees lower set-back periods.

Thing is, every house is different. Depends on how well insulated it is.

Best case scenario would be a well insulated box!

Thanks, thats sort of what I achieve, long but low output heating periods.

 

[Gary27]

It also depends on how concerned the owner is about using more gas than absolutely necessary.

If you dont need heating overnight ( like me ) then its more efficient turning the boiler on at 6.45 with a higher power setting instead of a lower power and turning it on two hours early and losing two hours of heating cost.

Or you can do what I do and change the max power setting from time to time during the day! But thats a bit anorackish!

Tony

So from that I take it that you are trying for a quick heatup in the morning and a low power gentle heat in the day. Why do you say losing two hours heating cost in the morning?

 

[Agile]

The cost of heating a property is pretty much the heat loss multiplied by the number of hours its hot!

Turning on the heating two hours before its needed is wasting two hours of heat.

A semi has a heat loss of about 10 kW. Each hour of heating to 21 C when -1 C outside uses about 12 kWh of power! Thats about 50p on a good tariff.

Tony

 

[Gary27]

The cost of heating a property is pretty much the heat loss multiplied by the number of hours its hot!

Turning on the heating two hours before its needed is wasting two hours of heat.

A semi has a heat loss of about 10 kW. Each hour of heating to 21 C when -1 C outside uses about 12 kWh of power! Thats about 50p on a good tariff.

Tony

OK get that, so idealy what you are saying is you want the house to temperature asap in the morning so when you are asleep it would be a waste, but in the day/evening run it on a low setting as you are in the house for that time.

 

[ALEC1]

no its not wasting heat... it depends what temperature you allow it to drop too...but running it at a lower temperature will save you money..

the problem is letting things (walls, furniture etc) get too cool requires more energy to heat up than just the air temp...you have to heat those things up too.

Where my clients have conducted experiments the consensus seems to be its no more expensive to heat 24/7 than turning on twice a day...but it depends on how long on those two periods are

and comfort is not just about air temp, its about other things such as humidity and the low level radiant heat of furniture and walls..

the good thing about the vrc 430 is that you can vary every parameter...

If it were me I would run the house at 17c when out and 20c in the morning and 21c in the evening...

 

[Gary27]

no its not wasting heat... it depends what temperature you allow it to drop too...but running it at a lower temperature will save you money..

the problem is letting things (walls, furniture etc) get too cool requires more energy to heat up than just the air temp...you have to heat those things up too.

Where my clients have conducted experiments the consensus seems to be its no more expensive to heat 24/7 than turning on twice a day...but it depends on how long on those two periods are

and comfort is not just about air temp, its about other things such as humidity and the low level radiant heat of furniture and walls..

the good thing about the vrc 430 is that you can vary every parameter...

If it were me I would run the house at 17c when out and 20c in the morning and 21c in the evening...

Thanks, that seems sensible.

 

[ALEC1]

at the end of the day...to save money don't use the heating...but to be comfortable you need the heating on... thats why you have heating....

heating has a cost...the best an installer can do is give you a system that if you engage with is efficient and keeps you warm...

I really would be running things to find the lowest temperature you are happy with...